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BMS 242 CVS & Respiration > Heart Electrophysiology > Flashcards

Heart Electrophysiology Flashcards

1
Q

What are intercalated disks composed of

A

desmosomes and gap junctions

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2
Q

What does electrical activity spread through

A

gap junctions

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3
Q

Where are gap junctions found

A

nodal cells, conducting cells and myocytes

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4
Q

Where is electrical activity initiated

A

sino atrial node

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5
Q

What is the function of sino atrial node

A

determine heart rate

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6
Q

Where is the sino atrial node located

A

right side, junction between superior vena cava and right atrium

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7
Q

Describe the pathway of electrical signals in the heart

A

right then left atrium, through the inter atrial tract to the AV node, down the bundle of His, into purkinje fibres to ventricular muscle cells

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8
Q

What does the spread of electrical activity occur through from right to left side

A

Bachmann’s bundle

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9
Q

Which atrium contracts fractionally faster than the other one

A

right atrium

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10
Q

What are the three subzones of the AV node

A

atrial nodal, nodal, nodal ventricular

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11
Q

Why does the electrical signal slow down at the AV node

A

generate an atrio ventricular delay - allows atria to finish contracting

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12
Q

What is the function of AV refractoriness

A

prevent excess ventricular contraction

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13
Q

What is the relationship between heart rate and AV refractoriness

A

inverse relationship

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14
Q

What is the effect of increased HR on AV node firing ability

A

as HR increases, ability of AV node to fire decreases

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15
Q

What is the effect of increased HR on AV refractoriness

A

increased HR increases AV refractoriness

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16
Q

Describe the pathway of electrical activitiy

A

specific pathway

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17
Q

What does the specific pathway of electrical activity create

A

spiral contraction - torsion

18
Q

Where does sub nodal contraction occur

A

bundle of His, Purkinje fibres and ventricular muscle

19
Q

Why is the twisting movement of heart contraction important

A

important for effective removal of blood

20
Q

What are the types of cardiac action potentials

A

nodal and contractile

21
Q

What exhibits nodal action potentials

A

SA node and AV node

22
Q

What exhibits contractile action potentials

A

atrial muscle, purkinje fibres and ventricular muscle

23
Q

TRUE or FALSE - all cardiac action potentials are different from nerve potentials

A

true

24
Q

What is characteristic about contractile action potentials

A

plateau phase at the peak of the action potential

25
Q

What cells do not have a resting membrane potential

A

pace maker cells

26
Q

What do pacemaker cells show

A

automaticity and rhythmicity

27
Q

Describe the membrane potential of pacemaker cells

A

resting membrane potential peaks at -60mV but instantly starts a slow depolarisation, then steep AP phase

28
Q

What causes pacemaker potential phase

A

reduction in potassium permeability

29
Q

What is the funny current mediated by

A

hyper polarisation induced channel HCN4

30
Q

What is slow depolarisation of pacemakers caused by

A

reduction in permeability to potassium

31
Q

What causes pacemaker action potential depolarisation

A

voltage gated calcium channels

32
Q

Which node is the more dominant

A

sino atrial node

33
Q

What is the effect of the sympathetic nervous system on pacemaker cells

A

increases prepotential slope, increases firing rate

34
Q

What is the effect of the parasympathetic system on pacemaker cells

A

hyperpolarisation, decreased pre potential slope

35
Q

Describe calcium release in the nodal cells

A

spontaneous release through ryanodine receptors

36
Q

What can calcium release cause in pacemaker cells

A

membrane depolarisation

37
Q

What is depolarisation mediated by in cardiac muscle

A

voltage gated sodium channels

38
Q

What is the plateau phase mediated by in cardiac muscle

A

voltage gated calcium channels

39
Q

What is the repolarisation phase mediated by in cardiac muscle

A

voltage gated potassium channels

40
Q

What is the sodium channel in the heart and AV myocytes

A

Nav1.5

41
Q

What is the main calcium channel in the heart

A

Cav1.2 (L-type calcium channel)

42
Q

What two channels mediate repolarisation in heart cells

A

HERG and KcLQT1

BMS 242 CVS & Respiration (10 decks)

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